This invention relates to clamping workbenches such as those of the type sold under the Trade Mark WORKMATE, and in particular to a secondary clamp for attachment thereto.
FIG. 19 of our UK Patent Application No. 9824243.1 illustrates one embodiment of a secondary clamp for attachment to a Workmate type clamping workbench which comprises a supplementary clamping jaw adapted to rest perpendicularly across the main jaws of a clamping workbench, with a single actuating arm, one end of which is adapted to be received in an opening in one of the jaws of the main clamping workbench and the other end of which is held captive in the supplementary jaw, and is pivotal relative thereto. In fact the joint between the end of the arm and the supplementary clamping jaw is a complex one and the arm not only pivots relative to the supplementary clamping jaw but is also slidable along upper and lower aligned slots in the supplementary clamping jaw, the direction of the slots being parallel to the length direction of the supplementary jaw and therefore being substantially perpendicular to the main jaws of the clamping workbench when the supplementary clamping jaw is fitted thereto.
Each of the main clamping workbench jaws is conventionally formed with a plurality of equally sized and equally spaced apart circular openings into which peg stops can be fitted to assist in clamping differently sized objects over the top of the jaws, as opposed to between the jaws. However from a study of FIG. 19 of our aforementioned Application it will be seen that there will be only a certain number of positions along the length of the main jaws of the clamping workbench at which the end of the pivoting arm can be inserted into an opening in one or the other of the main clamping workbench jaws, and if reliance is placed on jamming the other end of the arm at one end of the slots slot to achieve perpendicular movement of the supplementary clamping jaw relative to the closing or opening movement of the main jaws in accordance with the technique described in our earlier Application No. 9824243.1, there could be a number of xe2x80x9cblind spotsxe2x80x9d along the length of the main jaws at which it is not possible to obtain a reliable clamping movement of the supplementary jaw against a workpiece, or the two main jaws have to be moved undesirably close or far apart in order to achieve a clamping of the supplementary jaw relative to a workpiece.
For reference purposes, the positions along the length of the main jaws at which the supplementary jaw can be fitted across the main jaws with one end of the lever arm jammed at one end of the slots, and with the main jaws opened sufficiently to provide reliable support to the underside of a workpiece, will be referred to as primary clamping positions, and the position to which the supplementary jaw can be moved by a relatively small inward or outward movement of the main jaws so as to secure a clamping action on the workpiece, without significantly increasing or decreasing the gap between the two main jaws to an unacceptable amount, will be referred to as a secondary clamping position.
It is an object of the present invention to increase the number of primary and therefore secondary clamping positions in which a supplementary clamping jaw can be fitted between the main jaws of a clamping workbench, to increase the range of workpieces sizes which can be accommodated by such a supplementary clamping jaw.
According to one aspect of the invention in a clamping workbench as aforesaid, the inboard end of the actuating arm is pivotally securable in one of at least two spaced apart positions located along the length of the two aligned slots, and intermediate the ends thereof.
The invention envisages that the aligned slots extend either generally parallel or generally perpendicular to the workpiece engaging face of the supplementary jaw.
In a first embodiment of the invention, pairs of parking bays are provided at intervals along the length of the pair of aligned slots, for receiving therein the pin means at the inboard end of the actuating arm, each pair of parking bays defining a different pivoting position for the said inboard end of the arm.
Each pair of parking bays may comprise a pair of aligned lateral parking slots, one in the wall of each of the two aligned slots, each of which said lateral parking slots communicates with its aligned slot via an opening in the wall thereof, and subtends an angle of greater than 90xc2x0 to the length direction of the said aligned slot.
Each parking bay may include a second lateral parking slot, which diverges from the slot making up the first bay, but communicates with the aligned slot via a common opening, the two parking slots defining a letter V, with the vertex thereof comprising the common opening in the wall of the aligned slot, and with the V-shaped array of slots at each position along one aligned slot being aligned with a corresponding V-shaped array at the same position along the other aligned slot.
By providing the parking slots in the edge of a main aligned slots against which the pins protruding from the arm will press as the main clamping jaws are moved in a direction so as to clamp the supplementary jaw against a workpiece, whereby the act of clamping will push the pins into whichever pair of parking slots has been selected and there will be no tendency for the protruding pins to slide further along the length of the aligned slots in the supplementary jaw.
A plurality of such pairs of upper and lower aligned parking slots may be provided at intervals along the length of the main slots.
The angles selected for the parking slots relative to the aligned slots define the direction of movement needed of the protruding pins to enter the parking slots, and preferably this is selected so as to be approximately in the same direction as the direction of the thrust transmitted from the end of the arm anchored to one of the main clamping workbench jaws, along the length of the arm.
In a second embodiment, stop means may be provided for arresting the relative sliding of the pivoting connection between the arm and the supplementary jaw in a clamping workbench as aforesaid, so as to provide a range of positions along the length of the aligned slots in the supplementary jaw at which the end of the pivoting arm can be fixed.
The intermediate stop positions may be achieved by providing a plurality of drillings in the body of the supplementary jaw, each of the drillings extending across the slots above and below the cavity in which the inboard end of the arm is received, and by inserting pins into the drillings, so as to foreshorten the slots, so the extent of the travel along the length of the slots, by the pins, will be reduced.
If desired, two pairs of pins can be inserted so as to define a relatively short slot length within which the pins protruding from the arm can move.
In a third embodiment, elongate inserts can be provided for fitting into the aligned slots of the supplementary jaw again to restrict the length of the slots available to the pins protruding from the arm.
In this way it is not necessary for the inboard end of the pivoting arm always to travel to one end or the other of the aligned slots, but can if desired be located at intermediate positions between the ends of the slots so as to allow the user to jam the arm relative to the supplementary jaw at a plurality of different positions along the length of the slots to thereby increase the range of primary clamping positions for the supplementary jaw (and as a consequence its range of secondary positions) which can be achieved by a clamping or unclamping movement of the main clamping workbench jaws, whilst leaving the outboard end of the arm pivotally inserted in one opening in one of the main jaws of the clamping workbench.
According to another aspect of the invention, a peg which protrudes from the outboard end of the arm of a single arm supplementary clamping jaw as aforesaid, may be selectably insertable into one or other of two or more spaced apart openings along the length of the arm, to further increase the number of different positions at which clamping can be effected.
The invention also lies in a combination of the different aspects of the invention to provide an even greater range of variation in the primary clamping positions for the supplementary jaw, and therefore a corresponding increase in the number of secondary positions achievable by the jaw relative to any given pair of main clamping workbench jaws.
An important aspect of the invention lies in the fact that a large number of primary and secondary clamping positions for the supplementary jaw are still possible, particularly when both aspects of the invention are incorporated, even with a reduced number of peg stop openings in the main workbench jaws.